1 #include <sys/socket.h>
2 #include <netinet/in.h>
13 #include "stdio_impl.h"
17 static void cleanup(void *p)
19 __syscall(SYS_close, (intptr_t)p);
22 static unsigned long mtime()
25 clock_gettime(CLOCK_REALTIME, &ts);
26 return (unsigned long)ts.tv_sec * 1000
27 + ts.tv_nsec / 1000000;
30 int __res_msend(int nqueries, const unsigned char *const *queries,
31 const int *qlens, unsigned char *const *answers, int *alens, int asize)
35 unsigned char _buf[256];
36 char line[64], *s, *z;
37 int timeout = 5000, attempts = 2, retry_interval, servfail_retry;
39 struct sockaddr_in sin;
40 struct sockaddr_in6 sin6;
41 } sa = {0}, ns[3] = {{0}};
42 socklen_t sl = sizeof sa.sin;
50 unsigned long t0, t1, t2;
53 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
55 /* Get nameservers from resolv.conf, fallback to localhost */
56 f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
57 if (f) for (nns=0; nns<3 && fgets(line, sizeof line, f); ) {
58 if (!strncmp(line, "options", 7) && isspace(line[7])) {
61 p = strstr(line, "timeout:");
62 if (p && isdigit(p[8])) {
64 x = strtoul(p, &z, 10);
65 if (z != p) timeout = x < 30 ? x*1000 : 30000;
67 p = strstr(line, "attempts:");
68 if (p && isdigit(p[9])) {
70 x = strtoul(p, &z, 10);
71 if (z != p) attempts = x < 10 ? x : 10;
72 if (!attempts) attempts = 1;
75 if (strncmp(line, "nameserver", 10) || !isspace(line[10]))
77 for (s=line+11; isspace(*s); s++);
78 for (z=s; *z && !isspace(*z); z++);
81 if (__lookup_ipliteral(&iplit, s, AF_UNSPEC)>0) {
82 if (iplit.family == AF_INET) {
83 memcpy(&ns[nns].sin.sin_addr, iplit.addr, 4);
84 ns[nns].sin.sin_port = htons(53);
85 ns[nns++].sin.sin_family = AF_INET;
88 memcpy(&ns[nns].sin6.sin6_addr, iplit.addr, 16);
89 ns[nns].sin6.sin6_port = htons(53);
90 ns[nns].sin6.sin6_scope_id = iplit.scopeid;
91 ns[nns++].sin6.sin6_family = family = AF_INET6;
95 if (f) __fclose_ca(f);
97 ns[0].sin.sin_family = AF_INET;
98 ns[0].sin.sin_port = htons(53);
99 ns[0].sin.sin_addr.s_addr = htonl(0x7f000001);
103 /* Get local address and open/bind a socket */
104 sa.sin.sin_family = family;
105 fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
107 /* Handle case where system lacks IPv6 support */
108 if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
109 fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
112 if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) return -1;
114 /* Past this point, there are no errors. Each individual query will
115 * yield either no reply (indicated by zero length) or an answer
116 * packet which is up to the caller to interpret. */
118 pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
119 pthread_setcancelstate(cs, 0);
121 /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
122 if (family == AF_INET6) {
123 setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
124 for (i=0; i<nns; i++) {
125 if (ns[i].sin.sin_family != AF_INET) continue;
126 memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
127 &ns[i].sin.sin_addr, 4);
128 memcpy(ns[i].sin6.sin6_addr.s6_addr,
129 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
130 ns[i].sin6.sin6_family = AF_INET6;
131 ns[i].sin6.sin6_flowinfo = 0;
132 ns[i].sin6.sin6_scope_id = 0;
136 memset(alens, 0, sizeof *alens * nqueries);
140 retry_interval = timeout / attempts;
143 t1 = t2 - retry_interval;
145 for (; t2-t0 < timeout; t2=mtime()) {
146 if (t2-t1 >= retry_interval) {
147 /* Query all configured namservers in parallel */
148 for (i=0; i<nqueries; i++)
150 for (j=0; j<nns; j++)
151 sendto(fd, queries[i],
152 qlens[i], MSG_NOSIGNAL,
155 servfail_retry = 2 * nqueries;
158 /* Wait for a response, or until time to retry */
159 if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
161 while ((rlen = recvfrom(fd, answers[next], asize, 0,
162 (void *)&sa, (socklen_t[1]){sl})) >= 0) {
164 /* Ignore non-identifiable packets */
165 if (rlen < 4) continue;
167 /* Ignore replies from addresses we didn't send to */
168 for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
169 if (j==nns) continue;
171 /* Find which query this answer goes with, if any */
172 for (i=next; i<nqueries && (
173 answers[next][0] != queries[i][0] ||
174 answers[next][1] != queries[i][1] ); i++);
175 if (i==nqueries) continue;
176 if (alens[i]) continue;
178 /* Only accept positive or negative responses;
179 * retry immediately on server failure, and ignore
180 * all other codes such as refusal. */
181 switch (answers[next][3] & 15) {
186 if (servfail_retry && servfail_retry--)
187 sendto(fd, queries[i],
188 qlens[i], MSG_NOSIGNAL,
194 /* Store answer in the right slot, or update next
195 * available temp slot if it's already in place. */
198 for (; next<nqueries && alens[next]; next++);
200 memcpy(answers[i], answers[next], rlen);
202 if (next == nqueries) goto out;
206 pthread_cleanup_pop(1);